text: /**********************************************************************
   *
   * GEOS - Geometry Engine Open Source
   * http://geos.osgeo.org
   *
   * Copyright (C) 2020 Paul Ramsey <pramsey@cleverelephant.ca>
   *
   * This is free software; you can redistribute and/or modify it under
   * the terms of the GNU Lesser General Public Licence as published
   * by the Free Software Foundation.
   * See the COPYING file for more information.
   *
   **********************************************************************/
  
  #pragma once
  
  #include <geos/operation/overlayng/OverlayEdgeRing.h>
  
  #include <vector>
  #include <memory>
  #include <geos/export.h>
  
  // Forward declarations
  namespace geos {
  namespace geom {
  class Coordinate;
  class CoordinateArray;
  class GeometryFactory;
  }
  namespace operation {
  namespace overlayng {
  class OverlayEdge;
  class EdgeRing;
  }
  }
  }
  
  namespace geos {      // geos.
  namespace operation { // geos.operation
  namespace overlayng { // geos.operation.overlayng
  
  using namespace geos::geom;
  
  class GEOS_DLL MaximalEdgeRing {
  
  private:
  
      // Constants
      static constexpr int STATE_FIND_INCOMING = 1;
      static constexpr int STATE_LINK_OUTGOING = 2;
  
      // Members
      OverlayEdge* startEdge;
  
      // Methods
      void attachEdges(OverlayEdge* startEdge);
      void linkMinimalRings();
  
      /**
      * Links the edges of a {@link MaximalEdgeRing} around this node
      * into minimal edge rings ({@link OverlayEdgeRing}s).
      * Minimal ring edges are linked in the opposite orientation (CW)
      * to the maximal ring.
      * This changes self-touching rings into a two or more separate rings,
      * as per the OGC SFS polygon topology semantics.
      * This relinking must be done to each max ring separately,
      * rather than all the node result edges, since there may be
      * more than one max ring incident at the node.
      *
      * @param nodeEdge an edge originating at this node
      * @param maxRing the maximal ring to link
      */
      static void linkMinRingEdgesAtNode(OverlayEdge* nodeEdge, MaximalEdgeRing* maxRing);
  
      /**
      * Tests if an edge of the maximal edge ring is already linked into
      * a minimal {@link OverlayEdgeRing}.  If so, this node has already been processed
      * earlier in the maximal edgering linking scan.
      *
      * @param edge an edge of a maximal edgering
      * @param maxRing the maximal edgering
      * @return true if the edge has already been linked into a minimal edgering.
      */
      static bool isAlreadyLinked(OverlayEdge* edge, MaximalEdgeRing* maxRing);
  
      static OverlayEdge* selectMaxOutEdge(OverlayEdge* currOut, MaximalEdgeRing* maxEdgeRing);
      static OverlayEdge* linkMaxInEdge(OverlayEdge* currOut, OverlayEdge* currMaxRingOut, MaximalEdgeRing* maxEdgeRing);
  
  
  public:
  
      MaximalEdgeRing(OverlayEdge* e)
          : startEdge(e)
      {
          attachEdges(e);
      };
  
      std::vector<std::unique_ptr<OverlayEdgeRing>> buildMinimalRings(const GeometryFactory* geometryFactory);
  
      /**
      * Traverses the star of edges originating at a node
      * and links consecutive result edges together
      * into maximal edge rings.
      * To link two edges the resultNextMax< pointer
      * for an incoming< result edge
      * is set to the next outgoing result edge.
      *
      * Edges are linked when:
      * - they belong to an area (i.e. they have sides)
      * - they are marked as being in the result
      *
      * Edges are linked in CCW order
      * (which is the order they are linked in the underlying graph).
      * This means that rings have their face on the Right
      * (in other words,
      * the topological location of the face is given by the RHS label of the DirectedEdge).
      * This produces rings with CW orientation.
      *
      * PRECONDITIONS:
      * - This edge is in the result
      * - This edge is not yet linked
      * - The edge and its sym are NOT both marked as being in the result
      */
      static void linkResultAreaMaxRingAtNode(OverlayEdge* nodeEdge);
  
      friend std::ostream& operator<<(std::ostream& os, const MaximalEdgeRing& mer);
  
  };
  
  
  } // namespace geos.operation.overlayng
  } // namespace geos.operation
  } // namespace geos
  
  